Facilitation of avoidance learning by chlordiazepoxide-amphetamine combinations in mice

Diazepam promotes active avoidance extinction associating with increased dorsal CA3 and amygdala activity

Active avoidance (AA) is an adaptive response to potentially harmful situations while maladapted avoidance that does not extinguish is one of the core symptoms of anxiety and post-traumatic stress disorder. However, the neural mechanisms of AA extinction and its relationship to anxiety remain unclear. We examined AA extinction during three extinction training sessions in two-way active avoidance paradigm and tested the effect of anxiolytic on AA extinction. Then we performed a meta-analysis of rodent studies, identified anxiolytic diazepam facilitates AA acquisition, and tested the same treatment in AA extinction. Diazepam-treated rats significantly reduced avoidance in the first two extinction training, compared with the saline-treated rats, and the reduction in avoidance remained in the third drug-free session. Then we explored extinction associated hippocampal and amygdala activity in saline-and diazepam-treated rats using c-Fos immunostaining following the last extinction session. The density of c-Fos positive cells was higher in dorsal CA3 of the diazepam group than in that of saline-treated animals, and was also higher in the central and basolateral amygdala regions of diazepam-treated rats than in that of saline-treated animals. Combined, these results suggest anxiolytics promotes AA extinction associated with dorsal CA3 and amygdala activity changes.

Revisiting the role of anxiety in the initial acquisition of two-way active avoidance: pharmacological, behavioural and neuroanatomical convergence

Two-way active avoidance (TWAA) acquisition constitutes a particular case of approach -avoidance conflict for laboratory rodents. The present article reviews behavioural, psychopharmacological and neuroanatomical evidence accumulated along more than fifty years that provides strong support to the contention that anxiety is critical in the transition from CS (conditioned stimulus)-induced freezing to escape/avoidance responses during the initial stages of TWAA acquisition. Thus, anxiolytic drugs of different types accelerate avoidance acquisition, anxiogenic drugs impair it, and avoidance during these initial acquisition stages is negatively associated with other typical measures of anxiety. In addition behavioural and developmental treatments that reduce or increase anxiety/stress respectively facilitate or impair TWAA acquisition. Finally, evidence for the regulation of TWAA acquisition by septo-hippocampal and amygdala-related mechanisms is discussed. Collectively, the reviewed evidence gives support to the initial acquisition of TWAA as a paradigm with considerable predictive and (in particular) construct validity as an approach-avoidance conflict-based rodent anxiety model.

Impulsivity as a confounding factor in certain animal tests of cognitive function

Performance in cognitive tasks which require the subject to wait and/or to process a large amount of information can be disrupted by an increase in impulsive-like behaviour. Accordingly, a decrease in impulsive-like behaviour can improve performance in such tasks. Conversely, impulsive-like behaviour may improve performance in cognitive tasks where simple and fast responses and/or only little information processing is required. Thus, impulsivity constitutes a confounding factor in studies of cognitive function. Impulsive-like behaviour may be modified by serotonergic (5-HT) activity, with underactivity in 5-HT neurotransmission increasing impulsivity and vice versa. Drug- or lesion-induced alteration in 5-HT neurotransmission may, therefore, constitute suitable tools to investigate the role of impulsivity in animal tests of cognitive function. Benzodiazepines also increase impulsive-like behaviour, possibly by decreasing 5-HT neurotransmission. Hence, the effects of modulation of 5-HT systems and of the benzodiazepine-binding site on performance in animals tests of cognitive function will be discussed. It is predicted that the effects of manipulations of serotonergic activity or of benzodiazepine administration depend upon the nature of the response required, and that these effects may be mediated through changes in impulse control.

Infantile stimulation and the role of the benzodiazepine receptor system in adult acquisition of two-way avoidance behavior

The present study shows that postnatal "consistent" handling (CH) of rats had long-lasting improving effects on coping with an stressful task (i.e. two-way active avoidance), and that such effects were partially prevented by acute Ro 15-1788 (antagonist of benzodiazepine receptor-BZR; 5 mg/kg) administration. Long-lasting detrimental effects in the same task were also observed in rats which received postnatal "inconsistent" handling (INCH), effects that were slightly increased by acute Ro 15-1788 treatment. Finally, Ro 15-1788 tended to increase avoidance acquisition in non-handled (NH) animals. The observed effects of Ro 15-1788 could be partially attributed to a differential modulation of the process of avoidance acquisition depending on postnatal treatments producing different levels of emotionality.

Beneficial effects of infantile stimulation on coping (avoidance) behavior in rats are prevented by perinatal blockade of benzodiazepine receptors with Ro 15-1788

The present study shows that postnatal 'consistent' handling (CH; which consisted of removing the pups from the nest and placing them individually in plastic cages lined with paper towel for a period of 15 min daily between 1 and 22 postnatal days) of rats had long-lasting improving effects on coping with a stressful task (i.e. enhancement on the early acquisition of two-way active avoidance), but such effects were completely prevented when CH treatment was combined with chronic perinatal Ro 15-1788 (7 mg/kg/day, between prenatal day 19 and postnatal day 22) administration (i.e. blockade of benzodiazepine receptor (BZR)). A long-lasting decremental effect was also observed in the same task in rats which received postnatal 'inconsistent' handling (INCH; in which stimulation of pups was changed every day between 1 and 22 postnatal days), without being affected by the concomitant perinatal Ro 15-1788 treatment. These results suggest that intact ontogeny of BZRs is necessary to obtain the enduring positive effects of CH on emotional behavior (i.e. early acquisition of two-way active avoidance).

The early acquisition of two-way (shuttle-box) avoidance as an anxiety-mediated behavior: psychopharmacological validation

Several lines of evidence have established that performance during the initial steps of acquisition on a shuttle-box avoidance task is an anxiety-mediated behavior (i.e., the differences between strains selectivity bred for emotionality; the effects of postnatal handling; the course of the corticosterone response and behavioral measures of fear during acquisition). The present study was carried out to add pharmacological evidence to that view by testing the action of anxiogenic and anxiolytic drugs. Single 40-trial sessions with mild shocks (0.4 mA-0.6 mA) were used. In the first experiments the action of sodium pentobarbital (1.25, 2.5 and 5 mg/kg) and three benzodiazepines (diazepam, 2 and 4 mg/kg; alprazolam, 1, 1.25 and 1.5 mg/kg and adinazolam, 1, 2, 4 and 6 mg/kg) were tested. The last two experiments tested a possible proanxiety action of Ro 15-4513 (2, 5 and 10 mg/kg) and FG 7142 (5, 10 and 15 mg/kg), two partial inverse agonists of benzodiazepine receptors, which previous data had suggested to be anxiogenic. The results showed that the measure of acquisition of a two-way active avoidance is a sensitive mean for detecting either anxiolytic or anxiogenic effects of drugs, independently of their effects on locomotor activity, thus suggesting that such test could be a valid model of anxiety in animals.

Avoidance facilitation by chlordiazepoxide-amphetamine combinations in mice: effect of alpha-methyl-p-tyrosine

Chlordiazepoxide (CDP) and amphetamine (AMPH) were tested, alone or in combination, in BALB/c mice pretreated with alpha-methyl-p-tyrosine (AMT) and subjected to shuttle-box avoidance training. CDP and AMPH, given alone, partly reversed avoidance depression induced by 50 mg/kg of AMT, but were ineffective in mice pretreated with 100 mg/kg of AMT. Stronger effects were produced by CDP-AMPH combinations, which also improved avoidance performance in mice pretreated with the higher dose of AMT. The results suggest that catecholamines may play a role in the facilitation of avoidance induced by CDP, especially when given in combination with AMPH.

Enhancement by chlordiazepoxide of the anticholinergic-induced locomotor stimulation in mice

Spontaneous locomotor activity has been studied in mice treated with chlordiazepoxide, atropine, and scopolamine, given alone or in combination. Chlordiazepoxide alone increased activity for a short time, while the two anticholinergic drugs produced longer lasting stimulatory effects. Locomotor stimulation was stronger when chlordiazepoxide and anticholinergics were given in combination.

Facilitating effects of chlordiazepoxide on the performance of mice in an inhibitory avoidance task

Inhibitory avoidance behaviour of mice was studied by using an automated procedure. Animals were subjected to five 15-min sessions. Facilitation of the inhibitory avoidance behaviour was observed following the administration of chlordiazepoxide at doses which did not produce significant effects on spontaneous locomotor activity.

Facilitating effects of chlordiazepoxide on locomotor activity and avoidance behaviour of reserpinized mice

Chlordiazepoxide increased the spontaneous locomotor activity of both normal and reserpinized mice and facilitated the avoidance behaviour of mice pretreated with reserpine. These effects of chlorodiazepoxide on reserpinized animals were unexpected, since they are usually considered characteristic of antidepressant drugs.

Effects of chlordiazepoxide, amitriptyline, imipramine, and their combinations on avoidance behaviour in mice

Chlordiazepoxide, imipramine, and amitriptyline, given alone or in combination, were tested in mice subjected to 5 daily 100-trial avoidance sessions in the shuttle-box. When the drugs were given alone, chlordiazepoxide and the lower doses of imipramine facilitated avoidance behaviour. The higher doses of the two antidepressants impaired avoidance behaviour. Mixtures of chlordiazepoxide and imipramine produced some facilitating effects, while depressant effects prevailed in the chlordiazepoxide-amitriptyline combinations.